This invention relates to a capacitor structure and to a process for fabricating a capacitor structure.
DE 33 10 643 discloses a capacitor structure consisting of two substrates each having a capacitor electrode deposited thereon which is isolated from the respective substrate by an insulating layer. The distance between the capacitor electrodes is determined by a capping layer which is partly deposited on the capacitor electrodes and forms a dielectric of the capacitor. The two substrates are connected with one another using a bump technology. The capacitor structure is used as a pressure sensor.
A disadvantage of this capacitor structure is that it requires a spacing layer, namely the capping layer, to set the distance between the capacitor electrodes and hold the arrangement at this distance. The capacitance of the capacitor structure is determined by the thickness of the spacing layer, so that after deposition of the capping layer, variation of the capacitance is no longer possible. Furthermore, a variation of the thickness of the spacing layer causes a variation of the capacitance of the capacitor. In addition, the formation of the spacing layer requires additional photolithographic and etching steps which increase the complexity of the process. If a thick spacing layer is necessary, the process will be further complicated by the fact that the layer cannot be formed with standard thin-film processes.
The object of the invention is to provide a capacitor structure and a process for fabricating a capacitor structure whose capacitance is precisely adjustable over a wide range and which is easier to manufacture.
A capacitor structure including two substrates each having a capacitor electrode deposited on a surface, the substrates being joined together by bump structures located on both sides of the capacitor electrodes such that the capacitor electrodes lie opposite each other and form a capacitor, the distance d between the capacitor electrodes being defined by the height of the bump structures, and measuring connections being provided on one of the substrates for making capacitance measurements.